Light emission from Be and BeO surfaces bombarded by 5 keV Kr+ ions

Light emitted during the bombardment of beryllium and beryllium-oxide surfaces by 5 keV Kr+ ions is analyzed over the wavelength range 190–590 nm. A much larger photon yield is found when the target is an oxide. First, atomic lines are stronger. The analysis of their Doppler profile reveals the importance of collision sequences (Kr–O)–(O–Be) for the ejection of excited Be atoms. Secondly, a BeO target gives rise to luminescence. This is intense for medium angles of incidence and surprisingly declines steeply between 50° and 60°. Possible origins to luminescence are self-trapped excitons and F-centers. The intense emission from the BeO target contrasts with its absence for pure Be, which excludes radiation from surface plasmons. Bombardment of a BeO target also produces well-structured molecular bands.